There have been many efforts to capture and re-create human visual experience of being a location. Omni-directional photography is one way of effectively re-creating visual experience of a location at a specific moment. Omni-directional photograph may cover up to 360 degree horizontally and 180 degree vertically to cover whole spherical view from the photographing viewpoint.
However, to capture and re-create human visual experience, it is more efficient to concentrate capturing vicinity of horizontal viewing areas rather than trying to cover whole spherical view. For this reason, panoramic image, which omits upper part and lower part of spherical view, is also widely or generally used.
Currently, the prior-art methods to capture omni-directional images may be categorized as below:                (a) a method to cover about hemispheric viewing angle using non-planer mirror and a camera;        (b) a method to cover wider viewing angle using multiple planer mirror and multiple cameras;        (c) a method to generate a panoramic image by connecting a plurality of images which are obtained as a camera rotates;        (d) a method to produce a single image as by connecting a plurality of images which are obtained as a line-scan camera rotates (http://www.e-pan.com/index.html);        (e) a method to cover wider viewing angle by a plurality of imaged which are obtained as a plurality of cameras each of which covers different viewing angle (for example, U.S. Pat. No. 5,023,725); and        (f) a method to cover about hemispheric viewing angle using a camera with fisheye lens (for example, U.S. Pat. No. 5,185,667).        
Each method above has inherently advantages and disadvantages. The methods (a) and (f) tend to produce low-resolution image unless the image sensor of the camera is especially very big since they try to cover very wide viewing angle with single camera. Method (b) is hard to cover wide vertical viewing angle without using very big mirrors. Methods (c) and (d) capture omni-directional images over the camera rotating time so that moving object can be captured in different location of multiple images in method (c) or distorted in method (d). Method (e) utilized a plurality of cameras to cover wider viewing angle. In method (e), as the number of camera increases, each camera can cover less viewing angle and overall image resolution can be desirably enhanced.
However, when an image-capturing device adopting the method (e) is installed with a vehicle moving in normal driving speed and captures images, each camera of the image-capturing device can not be precisely controlled.
Some of the desired precise controls for image capturing while in fast motion are (1) precise synchronization of triggering of all cameras at the desired photographing location and (2) an adjustment of optimal exposure amount of each camera facing to different direction without creating motion blur.